1. Field of the Invention
The present invention relates to a nano-imprinting resin stamper that is pressed against a transfer target in order to form a micro structure (micropattern) on a surface thereof.
2. Description of the Related Art
Conventionally, a photolithography technique is often used for processing a micropattern that is necessary for semiconductor devices, etc. However, as the pattern becomes finer, it became difficult to cope with such fineness through the photolithography technique when a required processing dimension becomes small to the wavelength of light used for exposure. Therefore, an electron beam lithographic apparatus that is a kind of charged particle radiation apparatuses is recently used instead.
The pattern formation using the electron beam employs a method of directly drawing a mask pattern unlike a one-shot exposure method of the pattern formation using a light source, such as an i-ray and an excimer laser. Consequently, the more the number of patterns to be drawn is, the more it takes a time for exposure (drawing), and thus it takes a longer time to complete the pattern. The higher the integration degree of a semiconductor integrated circuit becomes, the more it requires a time for pattern formation, and thus reduction of a throughput must be concerned.
Hence, in order to speed up the electron beam lithographic apparatus, a one-shot pattern irradiation method is advanced which combines masks of various shapes and emitting electron beams at one time to those combined masks, thereby forming electron beam in a complex shape. In contrast, however, together with the advancement of the finer patterns, the electron beam lithographic apparatus increases its size, the mask position needs to be controlled highly precisely, and the apparatus cost increases.
Conversely, a nano-imprinting technique is known which forms a highly precise pattern at a lower cost. According to the nano imprinting technique, a stamper formed with concavity and convexity (a surface shape) corresponding to a micropattern to be formed is pressed against a transfer target obtained by, for example, forming a resin layer on a predetermined substrate, and the micropattern is transferred on the resin layer and is formed.
Moreover, when a stamper having a light transmissivity is used and pressed against the resin layer formed of a photo-curable resin, and such a resin layer is irradiated with light through the stamper, it is possible to make the resin layer cured.
Application of such nano-imprinting technique to a pattern formation of recording bits on a large-capacity recording medium, and to a pattern formation of semiconductor integrated circuits is discussed.
An example conventional stamper used for nano-imprinting and having a light transmissivity is a hard stamper of silica.
However, the hard stamper of silica has a problem such that it cannot follow a warpage of a transfer target substrate and a bump thereof, developing a transfer failure region across a broad range. Moreover, in order to reduce the transfer failure region, it is required for the stamper to absorb both warpage of the transfer target substrate formed with the resin layer and bump thereof. Hence, in order to follow both warpage of the transfer target substrate and bump thereof, there is proposed a stamper (a soft stamper) formed thickly of a soft resin (see, for example, JP 2010-5972 A). Such a soft stamper is capable of suppressing the transfer failure by following the warpage of the transfer target substrate and the bump thereof using the soft and think resin.
On the other hand, the demolding characteristic from a transfer target is important for the stamper used for the nano-imprinting technique. Conventionally, there is known a technique of applying a fluorine-based demolding agent to the surface of the hard stamper of silica (see, for example, JP 2004-351693 A). Moreover, stampers are also known which use a fluorine-based resin and silicone-based resin (see, for example, JP 2009-1002 A). According to the stamper with the demolding characteristic, the demolding from the transfer target is improved, and thus it is possible to improve the transfer precision of the micropattern to the transfer target.
However, the hard stamper of silica processed by the fluorine-based demolding agent is likely to develop a transfer failure as mentioned above. Moreover, regarding the stampers using the fluorine-based resin and silicone-based resin, the following capability to the warpage of the transfer target substrate and the bump thereof is still insufficient in comparison with the above-explained soft stamper, so that the transfer failure is not avoided sufficiently.
Therefore, the demolding treatment may be applied on the surface of the above-explained stamper.
However, since the soft stamper decreases the light transmissivity as the thickness thereof increases, there is a new problem such that a curing time of the above-explained photo-curable resin layer becomes long when irradiated with light (e.g., ultraviolet light with a wavelength of 365 nm) through the soft stamper. Moreover, the soft stamper that has the light transmissivity decreased reduces the transfer precision due to a thermal expansion originating from light absorbed.
In addition, when the demolding agent is applied on the surface of the soft stamper, the application thickness becomes uneven due to the wettability, etc., which accelerates reduction of the transfer precision. Moreover, the demolding layer formed on the surface of the soft stamper is likely to be deteriorated by repeating the transfer, and thus the so-called repetitive transfer characteristic also becomes insufficient.
Therefore, regarding the light-transmissive stamper used for the nano-imprinting technique, a nano-imprinting resin stamper is desired which has a sufficient light transmissivity for maintaining a good throughput, has an excellent transfer precision of a micropattern to a transfer target, and has an excellent repetitive transfer characteristic.
It is an object of the present invention to provide a nano-imprinting resin stamper which has a sufficient light transmissivity for maintaining a good throughput, has an excellent transfer precision of a micropattern to a transfer target, and has an excellent repetitive transfer characteristic, and a nano-imprinting apparatus using the same.